Water is often co-produced along with the production of petroleum oils, natural gas and condensate. In the case of off-shore production, such produced water, i.e., wastewater, is generally discharged to the body of natural water surrounding the producing platform structure. The wastewater may contain relatively high levels of environmentally contaminating materials that make the water unacceptable for discharge. Such materials include mercury and arsenic, along with varying concentrations of dissolved and dispersed hydrocarbons. The contaminant materials can be found in the water in the elemental or ionic forms. The dispersed hydrocarbons can be present as fine droplets contained in water in the form of an emulsion, i.e., emulsified hydrocarbons, or in the form of undissolved, yet non-emulsified hydrocarbons. Recent governmental regulations of such contaminating materials in the discharged wastewater set permissible concentrations and seek to reduce the contaminant levels to those that are environmentally innocuous. If the concentration of a contaminating material in the wastewater exceeds that specified in the regulations, the concentration of that contaminant must be reduced prior to discharge.
Accordingly, wastewater treatment processes are being developed to reduce the amount of contaminants in the wastewater to acceptable discharge levels, particularly processes feasible for use on off-shore hydrocarbon production platforms.